Question: Simplify the following expression: $q = \dfrac{r}{8} - \dfrac{r}{6}$
Answer: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $8$ and $6$ $\lcm(8, 6) = 24$ $ q = \dfrac{3}{3} \cdot \dfrac{r}{8} - \dfrac{4}{4} \cdot \dfrac{r}{6} $ $q = \dfrac{3r}{24} - \dfrac{4r}{24}$ $q = \dfrac{3r -4r}{24}$ $q = \dfrac{-r}{24}$